The preventable burden of endometrial and ovarian cancers in Australia: A pooled cohort study.

OBJECTIVE: Evidence on the endometrial and ovarian cancer burden preventable through modifications to current causal behavioural and hormonal exposures is limited. Whether the burden differs by population subgroup is unknown. METHODS: We linked pooled data from six Australian cohort studies to national cancer and death registries, and quantified exposure-cancer associations using adjusted proportional hazards models. We estimated exposure prevalence from representative health surveys. We then calculated Population Attributable Fractions (PAFs) with 95% confidence intervals (CIs), accounting for competing risk of death, and compared PAFs for population subgroups. RESULTS: During a median 4.9 years follow-up, 510 incident endometrial and 303 ovarian cancers were diagnosed. Overweight and obesity explained 41.9% (95% CI 32.3-50.1) of the endometrial cancer burden and obesity alone 34.5% (95% CI 27.5-40.9). This translates to 12,800 and 10,500 endometrial cancers in Australia in the next 10 years, respectively. The body fatness-related endometrial cancer burden was highest (49-87%) among women with diabetes, living remotely, of older age, lower socio-economic status or educational attainment and born in Australia. Never use of oral contraceptives (OCs) explained 8.1% (95% CI 1.8-14.1) or 2500 endometrial cancers. A higher BMI and current long-term MHT use increased, and long-term OC use decreased, the risk of ovarian cancer, but the burden attributable to overweight, obesity or exogenous hormonal factors was not statistically significant. CONCLUSIONS: Excess body fatness, a trait that is of high and increasing prevalence globally, is responsible for a large proportion of the endometrial cancer burden, indicating the need for effective strategies to reduce adiposity.

The preventable burden of breast cancers for premenopausal and postmenopausal women in Australia: A pooled cohort study.

Estimates of the future breast cancer burden preventable through modifications to current behaviours are lacking. We assessed the effect of individual and joint behaviour modifications on breast cancer burden for premenopausal and postmenopausal Australian women, and whether effects differed between population subgroups. We linked pooled data from six Australian cohort studies (n = 214,536) to national cancer and death registries, and estimated the strength of the associations between behaviours causally related to cancer incidence and death using adjusted proportional hazards models. We estimated exposure prevalence from representative health surveys. We combined these estimates to calculate Population Attributable Fractions (PAFs) with 95% confidence intervals (CIs), and compared PAFs for population subgroups. During the first 10 years follow-up, there were 640 incident breast cancers for premenopausal women, 2,632 for postmenopausal women, and 8,761 deaths from any cause. Of future breast cancers for premenopausal women, any regular alcohol consumption explains 12.6% (CI = 4.3-20.2%), current use of oral contraceptives for ≥5 years 7.1% (CI = 0.3-13.5%), and these factors combined 18.8% (CI = 9.1-27.4%). Of future breast cancers for postmenopausal women, overweight or obesity (BMI ≥25 kg/m2 ) explains 12.8% (CI = 7.8-17.5%), current use of menopausal hormone therapy (MHT) 6.9% (CI = 4.8-8.9%), any regular alcohol consumption 6.6% (CI = 1.5-11.4%), and these factors combined 24.2% (CI = 17.6-30.3%). The MHT-related postmenopausal breast cancer burden varied by body fatness, alcohol consumption and socio-economic status, the body fatness-related postmenopausal breast cancer burden by alcohol consumption and educational attainment, and the alcohol-related postmenopausal breast cancer burden by breast feeding history. Our results provide evidence to support targeted and population-level cancer control activities.

Reoperation after breast-conserving surgery for cancer in Australia: statewide cohort study of linked hospital data.

OBJECTIVES: To investigate between-hospital variation in the probability of reoperation within 90 days of initial breast-conserving surgery (BCS), and the contribution of health system-level and other factors. DESIGN: Population-based, retrospective cohort study. SETTING: New South Wales (NSW), Australia. PARTICIPANTS: Linked administrative hospitalisation data were used to define a cohort of adult women undergoing initial BCS for breast cancer in NSW between 1 July 2002 and 31 December 2013. PRIMARY OUTCOME MEASURES: Multilevel, cross-classified models with patients clustered within hospitals and residential areas were used to examine factors associated with any reoperation, and either re-excision or mastectomy, within 90 days. RESULTS: Of 34 458 women undergoing BCS, 29.1% underwent reoperation within 90 days, half of which were mastectomies. Overall, the probability of reoperation decreased slightly over time. However, there were divergent patterns by reoperation type; the probability of re-excision increased alongside a concomitant decrease in the probability of mastectomy. Significant between-hospital variation was observed. Non-metropolitan location and surgery at low-volume hospitals were associated with a higher overall probability of reoperation, and of mastectomy specifically, after accounting for patient-level factors, calendar year and area-level socioeconomic status. The magnitude of association with geographical location and surgical volume decreased over time. CONCLUSIONS: Reoperation rates within 90 days of BCS varied significantly between hospitals. For women undergoing mastectomy after BCS, this represents a dramatic change in clinical course. Multilevel modelling suggests unwarranted clinical variation may be an issue, likely due to disparities in access to multidisciplinary breast cancer care and preoperative diagnostic procedures. However, the observed reduction in disparities over time is encouraging and indicates that guidelines and policy initiatives have the potential to improve regional breast cancer care.